This invention relates to a method of lubricating a plurality of compressed air operated devices, for instance motors, that are independently supplied with compressed air. The invention relates also to a lubricant furnishing system for carrying out the method.
The most common way of lubricating compressed air consuming devices--for instance the devices of a rock drilling rig--is to add the lubricating oil to the compressed air by means of venturi nozzles that are connected upstream of the supply valves that control the air to the compressed air consumers. On practical grounds, the supply valves must be located at a distance from the consumers and this fact alone, makes the lubrication ununiform. Still more ununiform it will be if two or more consumers have a common supply valve, which is not unusual. Further, one inherent disadvantage of the venturi principle of lubrication is that the lubricant is added substantially in proportion to the amount of air consumed. Therefore, there must be an average over-supply of lubricant in order to provide adequate lubrication always. It has been suggested instead to use a piston pump integral with an oscillating compressed air piston motor for each consumer. This piston pump is then powered by air from the supply line of the consumer for instance the supply line of the rock drill, and it starts therefore automatically when the rock drill is started. Not only is it expensive to use a pump with motor for each device that is to be lubricated but the lubrication will be ununiform since the pressure in the supply line of for instance a rock drill mounted on a rock drilling rig usually varies substantially so that the drive pressure of the compressed air actuated piston of the lubricator will also vary.
It is an object of the invention to make possible a more precise and accurate dispensing of lubricant to compressed air powered devices than has been possible hitherto. To this end, the invention has been given the characteristics stated in the claims.